Graphical representation of a wafer processing process

ABSTRACT

A method for graphically representing the progress of wafers being processed in a plurality of process stations is disclosed. In one step, the start of a process performed on the wafers in one of the plurality of process stations is determined. Then, the generation of a first line segment parallel to a first axis is initiated. Next, the end of the process in one of the plurality of process stations is determined. Then the generation of the first line segment parallel to the first axis is terminated. The start of a transfer of the wafers from one of the plurality of process stations to another one of the plurality of process stations is detected in a next step. Then, the formation of a second line segment connected with the first line segment and substantially perpendicular to the first axis is initiated. The completion of the transfer of the wafers is then determined and the formation of the second line segment perpendicular to the first axis is terminated. The process is then repeated for each process station until the wafers have been processed through all the process stations.

TECHNICAL FIELD

[0001] This invention relates to the field of semiconductormanufacturing and more specifically to a method of graphicalrepresentation of a wafer processing process.

BACKGROUND OF THE INVENTION

[0002] In automated fabrication plants or inside a complexwafer-processing tool, work pieces travel from one process station toanother. At these process stations various operations are performed onthe work pieces. Some process stations perform operations on the workpieces for a longer period of time than other process station. Also,some process stations are able to operate on a larger number of workpieces than other process stations. Additionally, the time taken totransfer the work pieces between process stations is an importantfabrication parameter. One difficulty in monitoring the progress of workpieces in fabrication plants is that information involving plantprocesses is not provided in a manner that allows an operator to quicklyvisualize plant or tool parameters in an easy to use and efficientmanner. Also, there are no simple ways to use simulated data, eithergenerated by a simulation machine or generated using knowledge of plantparameters, to produce a visual representation of a processing processfor planning purposes.

[0003] To overcome this problem, different process visualization schemeshave been proposed. One scheme is disclosed in U.S. Pat. No. 6,099,598issued to Yokoyama on Aug. 8, 2000. This invention discloses a method ofdisplaying a semiconductor manufacturing process. The display shows thetransportation of a semiconductor wafer and the processing of thesemiconductor wafer on a horizontal line. Additional wafers areillustrated on other horizontal lines, one line on top of another. Thisapproach, however, makes it difficult to see what process station thewafer is in. Additionally, it does not give an indication of thequantity of wafers in a process station.

[0004] Another scheme is detailed in U.S. Pat. No. 6,230,068 and issuedto Wu et al on May 8, 2001. This patent discloses the collection of datafrom different stages of a process line. The data from each stage isplaced on a bar chart. The bar charts are arranged in pairs representingprocess steps. However, these charts do not indicate what processstation a work piece is in, do not indicate when work pieces aretransferred and do not indicate the quantity of work pieces at eachprocess station at a given time.

[0005] In view of the problem, described above, the need remains for agraphical representation of a processing process that provides a simpleway to determine plant parameters.

SUMMARY OF THE INVENTION

[0006] Thus, a need has arisen for a method and system to produce agraphical representation of a wafer processing process that overcomesdisadvantages associated with other graphical representations.

[0007] In one embodiment, a method for graphically representing theprogress of wafers being processed in a plurality of process stations isdisclosed. In one step, the start of a process performed on the wafersin one of the plurality of process stations is determined. Then, thegeneration of a line segment parallel to a first axis is initiated.Next, the end of the process in one of the plurality of process stationsis determined. Then the generation of the line segment parallel to thefirst axis is terminated. The start of a transfer of the wafers from oneof the plurality of process stations to another one of the plurality ofprocess stations is detected in a next step. Then, the formation of aline segment substantially perpendicular to the first axis is initiated.The completion of the transfer of the wafers is then determined. Theformation of the line segment perpendicular to the first axis isterminated. The process is then repeated for each process station untilthe wafers have been processed through all the process stations.

[0008] In another embodiment, a display for displaying a graphicalrepresentation of a process involving a plurality of process stations inthe manufacture of one or more work pieces is provided. The displayincludes a graph area to display the graphical representation. Thegraphical representation includes a plurality of line segments in afirst direction. The length of the line segments in the first directionindicates the time one or more work pieces spend in one of the pluralityof process stations. Also, the graphical representation includes aplurality of line segments in a second direction. The line segments inthe second direction connect the line segments in the first direction.Also, the line segments in the second direction represent the transferof one or more work pieces from one of the plurality of process stationsto another one of the plurality of process stations.

[0009] In another embodiment, a manufacturing system is disclosed. Themanufacturing system includes a process tool having a plurality ofprocess stations that perform manufacturing steps on a plurality of workpieces. The manufacturing system includes a controller coupled to theprocess tool to send control commands to the process tool. A display iscoupled to the controller. The display receives data from the controllerregarding the processing of the plurality of work pieces in the processtool. The display includes a display area to display a graphicalrepresentation of the processing of the work pieces. The graphicalrepresentation includes a plurality of line segments in a firstdirection. The length of the line segments in the first directionindicates the time one or more work pieces spend in one of the pluralityof process stations. Also, the graphical representation includes aplurality of line segments in a second direction. The line segments inthe second direction connect the line segments in the first direction.Also, the line segments in the second direction represent the transferof one or more work pieces from one of the plurality of process stationsto another one of the plurality of process stations.

[0010] Also, a program product for displaying a graphical representationof a process is provided. The program product includes a computerreadable storage medium for storing instructions that, when executed bya computer causes the computer to perform a method for generating agraphical representation of a processing system in which one or morework pieces are processed in a number of process stations. The programproduct includes computer readable program code for forming a first linesegment in a first direction, the first line segment indicating the timeone or more work pieces spend in a first process station. Also includedis computer readable program code for forming a second line segmentconnected to the first line segment in a second direction, the secondline segment representing the transfer of the one or more work piecesfrom the first process station to a second process station.

[0011] Technical benefits of the present invention include forming agraphical representation of a process that shows both the time a workpiece is in a process station and the transfer of work piece fromstation to station. Other technical benefits are apparent from thefollowing descriptions, illustrations and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Non-limiting and non-exhaustive preferred embodiments of thepresent invention are described with references to the following figureswherein like reference numerals refer to like parts throughout thevarious views unless otherwise specified.

[0013]FIG. 1 is a block diagram of a manufacturing system;

[0014]FIG. 2 is a schematic drawing of a cluster tool;

[0015]FIG. 3 is a drawing of an exemplary graphical representation ofprocesses in a cluster tool; and

[0016]FIG. 4 is a flow chart illustrating steps in the generation of thegraphical representation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A method of the present invention includes a method to displaydata from a system in which one or more work pieces undergo differentprocessing steps in a number of different processing stations. Themethod can be used in any one of a number of systems where work piecesare processed in different processing stations. The example presented inthe following figures are for illustrative purposes only and are notintended to limit the application of the present invention to suchexamples.

[0018] For example, FIG. 1 is a block diagram of a manufacturing system10 in accordance with the teachings of the present invention.Manufacturing system 10 includes a process tool 12 coupled to acontroller 16 via input/output line 14 and a display 20 coupled to thecontroller 16 via input/output line 18.

[0019] Processing tool 12 may be any tool wherein a work piece, such asa semiconductor wafer, undergoes multiple processing steps. Each of theprocessing steps performed by processing tool 12 will typically beperformed in a processing station that is provided as part of theprocess tool 12.

[0020] Controller 16 can be any device capable of sending commands toprocessing tool 12 in order to control the operation and functionalityof processing tool 12. Controller 16 may include a memory for storing aprocessing tool control program and a processor for executing theprocess tool control program. Controller 16 may be a proprietary deviceor may be implemented using a general-purpose computer. An example of ageneral purpose computer is a personal computer based on an INTELprocessor such as the PENTIUM family of processors and running anoperating system such as DOS, OS2, or Windows 3.1, 95, 98, ME, NT, 2000,XP or the like. Such a general-purpose computer could interface withadditional controllers within processing tool 12. Controller couplesprocessing tool 12 via input/output line 14. Input/output line 14 can beany type of data connection, wired or wireless.

[0021] Display 20 couples to controller 16 via input/output line 18 andreceives information regarding the processing of a work piece in processtool 12. Display 20 can then display a novel graphical representation ofthe progress of the processing of the work piece in process tool 12 asfurther described in conjunction with FIGS. 3 and 4. Input/output line18 can be any connection, wired or wireless, that permits the transferof data between controller 16 and display 20. Input/output line 18 canbe a connection over a local or wide area network to allow for theremote viewing of processing data.

[0022] Display 20 may be a display integrated as part of a controlconsole that can include controller 16 for process tool 12. In thisembodiment, control information may be sent back to process tool 12 viacontroller 16. Display 20 may be a conventional cathode ray tube (CRT)monitor, a liquid crystal display (LCD) or plasma monitor, a printercapable of graphical output and the like.

[0023] Display 20 may also be coupled to a simulator of a process tool12. The simulator generates simulation data regarding the processing ofa work piece using a simulation program, running on a computer. Thesimulation data would then be displayed using a novel graphicalrepresentation as discussed in greater detail below. In anotherembodiment, the simulation data can be generated using a combination ofa simulation program running on a computer and manual steps.

[0024] An example of a process tool 12 is shown in FIG. 2. FIG. 2 is aschematic diagram of a cluster tool 100. Cluster tool 100 is one of manypossible process tools 12 that can be used with the present inventionand are well known in the art. Cluster tool 100 includes a number ofprocess stations coupled to a central wafer-handling chamber 106. In anexemplary system process stations include a first input/output chamber102 and a second input/output chamber 104 coupled to a centralwafer-handling chamber 106. Also included are a HF etching station 108,a staging station 110, an oxidation station 112, and a low-pressurechemical vapor deposition (LPCVD) station 114. Each process station, aswell as the wafer-handling chamber 106, may be equipped with sensors(not \pictured) that can indicate the presence or removal of wafers 118.While FIG. 2 shows a specific configuration of a cluster tool 100, otherconfigurations may be used in conjunction with the present invention.

[0025] First input/output station 102 and second input/output station104 each hold one or more carriers 116. Each carrier 116 holds aplurality of wafers 118. In one embodiment each input/output chamber102, 104 holds two carriers 116 stacked on top of each other. Eachcarrier 116 holds twenty-five wafers 118 per carrier 116. Thus, a totalof one hundred wafers 118 can be processed in one group or batch throughcluster tool 100. First input/output chamber 102 and second input/outputchamber 104 include sensors that detect the presence of carriers 116.Carriers 116 can be scanned by using well-known techniques to determinewhich slots of the carrier 116 wafers 118 occupy.

[0026] Wafer handling chamber (WHC) 106 includes a robot arm 120. Robotarm 120 moves wafers 118 from carriers 116 to the process stations108-114. Robot arm 120 also moves wafers between stations 108-114. Waferhandling chamber 106 and robot arm 120 are conventional parts of a waferprocessor machine. Robot arm 120 may also include a sensor (notpictured) for detecting the presence or absence of wafers 118 on robotarm 120. The sensors associated with robot arm 120 can be used to trackthe insertion or removal of wafers 118 from a process station, which inturn tracks the movement of wafers 118 throughout cluster tool 100.

[0027] HF etching station 108 is coupled to wafer handling chamber 106.In a typical embodiment, HF etching station 108 can process twenty-fivewafers 118 at a time. The HF etching station 108 uses hydrogen fluorideto clean the surface of the wafers 118. Staging station 110 holds thewafers between certain processing steps. Oxidation station 112 is alsocoupled to wafer handling chamber 106. In oxidation station 112 a thinlayer of oxide is formed over the surface of wafers 118. LPCVD station114 is coupled to wafer handling chamber 106. LPCVD station 114 applieslayers on to the surface of the wafer 118 such as a layer of siliconnitride for passivation or other purposes. All of these process stationsare conventional process stations well known in the design of clustertools. Each process station may also include sensors to determine thenumber of wafers 118 present at each process station. While FIG. 2illustrates the use of certain process stations, other stations can beused with the present invention.

[0028] In operation, in one embodiment, first input/output chamber 102and second input/output chamber 104 each have two carriers 116 withtwenty-five wafers 118 per carrier 116. The total amount of wafers 118that will be processed together is known as a batch. In the embodimentdescribed, one batch is one hundred wafers 118. Initially, robot arm 120in wafer handling chamber 106 moves wafers 118 from one of the carriers116 of input/output chamber 102 to HF etching station 108 where wafers118 are etched. HF etching station 108, in one embodiment, can etchtwenty-five wafers 118 at a time. After twenty-five wafers 118 areetched, they are transported by robot arm 120 to staging station 110.Then, another twenty-five wafers 118 are transferred by robot arm 120from one of the input/output chambers 102, 104 to HF etching station 108for an HF etch. This continues until all wafers 118 in carriers 116 areprocessed through HF etching station 108 and transferred to stagingstation 110.

[0029] After all wafers 118 have been processed in HF etching station108 and placed in staging station 110, they are transferred by robot arm120 to oxidation station 112. In one embodiment, oxidation station 112holds and oxidizes one hundred wafers 118 simultaneously.

[0030] After the oxidation process is complete, wafers 118 aretransferred by robot arm 120 from oxidation station 112 to LPCVD station114 where a layer of silicon nitride or other material is deposited ontothe wafers 118. In one embodiment, LPCVD station 114 holds and processesone hundred wafers 118 simultaneously. After the LPCVD process iscomplete, wafers 118 are transferred back to staging chamber 110. Aftersufficient cool-down, wafers 118 are transferred from staging station110 back to input/output chambers 102 and 104. While specific processstations are shown in FIG. 2, these are used as illustrations only andany process station can be used. Additionally, although a cluster tool100 is illustrated in FIG. 2, the present invention can be used for avariety of processing environments in which one or more work pieces areprocessed through various process stations.

[0031]FIG. 3 illustrates a graphical display 200 that graphicallydepicts the progress of wafers being processed in a process tool 12,such as cluster tool 100. Graphical display 200 is displayed on display20. Display 20 may be coupled to a process tool 12, such as cluster tool100 for observation by an operator of the process tool 12.Alternatively, graphical display 200 may be displayed on a display 20coupled to a computer running a simulation of a cluster tool 100. Also,graphical display 200 can be generated manually using, in oneembodiment, conventional drawings or computer aided design (CAD)software such as VISIO by Microsoft. Manual generation of graphicaldisplay 200 is useful when an operator is initially defining the optimalconfiguration of a cluster tool 100 or the like.

[0032] A process station area 202 is included in graphical display 200.In the embodiment shown in FIG. 3 process station area 202 includes thename of each process station in cluster tool 100 listed in a column.Process station area 202 forms an axis of the graphical display 200. Anoccupancy area 206 is included in graphical display 200, typicallyadjacent to process station area 202 and is used to indicate theoccupancy of a process station as a percentage of time where 100%occupancy means that a process station is occupied all the time. In anoptimum configuration, all process stations will have similar occupancy.When each station has similar occupancy there are no bottlenecks in theprocess. A time scale area 208 is included in graphical display 200.

[0033] Time scale area 208 includes time increments and provides asecond axis for graphical display 200. In FIG. 3, time scale area 208 isaligned along a horizontal axis. The time increments typically arelisted in increments of minutes, although other time scales can be used.

[0034] A graph area 210 is included in graphical display 200. Graph area210 may include one or more graphical representations of a process, suchas the movement and processing of a batch of wafers through the clustertool. In FIG. 3 there is a first graph 212, a second graph 214 and athird graph 216. Only second graph 214 is shown in its entirety. Todistinguish between multiple graphs different colors or shading schemescan be used for each different graph.

[0035] First graph 212; second graph 214 and third graph 216 comprise aseries of horizontal line segments 205 and vertical line segments 207 ofvarying thickness. In one embodiment the horizontal line segments 205and vertical line segments 207 are connected. The length of thehorizontal line segments 205 represents the amount of time wafers spendin a process station. The vertical thickness of the horizontal linesegments 205 is indicative of the number of wafers in a process stationat a given time. The thicker the horizontal line segment 205, the morewafers present.

[0036] The length of the vertical line segments 207 represent thetransfer of wafers from one process station to another process station.The horizontal width of the vertical line segment 207 represent theamount of time it takes to complete the transfer. While FIG. 3 has thetime scale along a horizontal direction and the process stations listedin a vertical direction, different orientations can be used.

[0037] Turning to the second graph 214 and using the cluster tool 100 ofFIG. 2 as an exemplary process tool 12, a quantity of wafers 118 areinitially loaded into first input/output chamber 102 and secondinput/output chamber 104. In one embodiment, first input/output chamber102 and second input/output chamber 104 each hold fifty wafers 118 intwo carriers 116 of twenty-five wafers 18 each. The initial conditionfor first input/output chamber 102 is depicted as point 3 a of secondgraph 214. The thickness of the horizontal line segment 205 at thispoint is proportional to the number of wafers 118 in the firstinput/output chamber 102. At point 3 b, the wafers 118 of one of the twocarriers 116 of first input/output chamber 102 are transferred by robotarm 120 to HF etching station 108. The HF etching station 108 initiatesits etching process at point 3 c. The thickness of the vertical linesegment 207 from point 3 b to point 3 c represents the amount of timeneeded to transfer the wafers 118 of carrier 116 from first input/outputchamber 102 to HF etching station 108. The vertical line segment 207from point 3 b to 3 c represents the transfer of wafers from one processstation to another. At point 3 b the horizontal line segment 205representing the presence of wafers 118 in first input/output chamber102 is connected to the vertical line segment 207 representing theinitiation of the transfer of wafers 118 to HF etching station 108.Point 3 c represents the end of the transfer of wafers 118 to the HFetching station 108. Point 3 d indicates where the HF etching processends for the wafers 118 of the first carrier 116 of first input/outputchamber 102. After the HF process ends for wafers 118 of the firstcarrier 116 of first input/output chamber 102, these wafers 118 aretransferred to staging station 110. Line segment 3 d to 3 e illustratesthe transfer of these wafers 118 from HF etching station 108 to stagingstation 110.

[0038] The wafers 118 of the second carrier 116 of first input/outputchamber 102 are transferred starting at point 3 f and ending at point 3g to HF etching station 108. The wafers 118 of second carrier 116 offirst input/output chamber 102 are in HF etching station 108 from thetime between points 3 g to 3 h. Then, from point 3 h to point 3 i wafers118 of the second carrier 116 of first input/output chamber 102 aretransferred to staging station 110. Note that at point 3 i the thicknessof the horizontal line segment increases, indicating that twice as manywafers 118 are in staging station 110 after wafers 118 of the secondcarrier 116 of first input/output chamber 102 are transferred to stagingstation 110.

[0039] Turning now to second input/output chamber 104, at point 3 jwafers 118 in first carrier 116 of second input/output chamber 104 startthe transfer process from the second input/output chamber 104 to HFetching station 108. At point 3 k the transfer finishes. The wafers 118of second input/output chamber 104 are in HF etching station 108 fromthe time between points 3 k to 31. Then, from point 31 to point 3 mwafers 118 from first carrier 116 of second input/output chamber 104 aretransferred to staging station 110. Note that at point 3 m the thicknessof the horizontal line segment increases over that at point 3 i,indicating that more wafers 118 (in the example seventy-five wafers 118)are in staging station 110.

[0040] The wafers 118 of the second carrier 116 of second input/outputchamber 104 are transferred starting at point 3 n and ending at point 3o to HF etching station 108. Wafers 118 of second carrier 116 of secondinput/output chamber 104 are in HF etching station 108 from the timebetween point 3 o to 3 p. Then, from point 3 p to point 3 q wafers 118of the second carrier 116 of second input/output chamber 102 aretransferred to staging station 110.

[0041] After all wafers 118 are in staging station 110, they aretransferred, starting at point 3 q, to oxidation station 112 by robotarm 120, where an oxidation process starts at point 3 r. All of thewafers 118 are transferred to oxidation station 112 at point 3 r. Atoxidation station 112, wafers 118 undergo an oxidation process that lastfrom point 3 r to 3 s. At point 3 s, robot arm 120 transfers all wafers118 from oxidation station 112 to LPCVD station 114, which starts atpoint 3 t. The line segment between point 3 t and point 3 u representsthe amount of time wafers 118 spend in LPCVD station 114. The actualprocess time in LPCVD station 114 is denoted as the length of the linesegment between 3 t and 3 u′. The time between 3 u′ and 3 u representsthe time the wafers are in LPCVD station 114 but are not able to leavethe station because wafer handling chamber 106 is in use. At point 3 u,wafer handling chamber 106 is available and the wafers 118 aretransferred back to staging station 110. The transfer process last frompoint 3 u to 3 v. All of wafers 118 are transferred back to stagingstation 110. Then, beginning at point 3 w and ending at point 3 x,wafers 118 are transferred back to carriers 116 in first input/outputchamber 102. After that, beginning at point 3 y to point 3 z, theremaining wafers 118 are transferred to two carriers 116 in secondinput/output chamber 104.

[0042] From second graph 214 various process parameters can bedetermined. For example at time=0 the processing of wafers for secondgraph 214 initiates. At time=490 minutes the processing of wafers forsecond graph 214 finishes. Thus, the total amount of time wafers 118 arein cluster tool 100 is 490 minutes. The time the wafers 118 are in thecluster tool 100 is known as the cycle time for the system.Additionally, the length of the vertical line segments in the horizontaldirection indicates the amount of time wafers 118 are in a specificprocessing module. Also, the thickness of horizontal line segmentsrepresents the number of wafers present at a process station. Thehorizontal line segments and vertical line segments can be connected toeach other to show a continuous process.

[0043] Also illustrated in graph area 210 is first graph 212. At time=0,first graph 212 shows the movement of wafers 118 from oxidation station112 to LPCVD station 114. Note that at approximately time=110, there isa dotted box 232 in the horizontal line segment representing the LPCVDprocess of the first graph 212. Dotted box 232 represents wafers 118that have completed the LPCVD process but are still in the LPCVD station114 because the wafers 118 cannot be unloaded. The wafers 118illustrated in first graph 212 cannot be unloaded because robot arm 120is occupied moving wafers associated with the process shown in secondgraph 214. Note that at the time when dotted box 232 exists in firstgraph 212, the wafers 118 associated with the second graph 214 areeither being loaded into the staging station 110 or are beingtransferred from the staging station 110 during the time the wafers 118associated with first graph 212 are waiting in the LPCVD station 114.The dotted box 232 allows an operator to see where a process in onebatch is holding up another process for another batch.

[0044] Also illustrated is a third graph 216, which initiates at t=290.Wafer transfer for third graph 216 initiates once all the wafers insecond graph 214 are transferred to the LPCVD station 114 at point 3 t.The number of wafers in a batch divided by the time elapsed between theinitiation of processing for one batch of wafers and the initiation ofprocessing for a second batch of wafers is the throughput. In theexample in FIG. 3 the throughput is 100 wafers divided by 290 minutes,or .344 wafers/minute, which is equivalent to 20.7 wafers/hour.

[0045] To maximize the use of resources, new carriers 116 with wafers118 should be loaded into the first input/output chamber 102 and secondinput/output chamber 102 as soon as possible. In the above example,turning to second graph 214, as soon as the last wafer 118 is loadedinto the HF station 108 it would be desirable to load new carriers 116with new wafers 118 into the first and second input/output chamber 102,104. In the example of FIG. 3, the last wafer 118 of the second graph214 is loaded into HF etching station 108 at point 3 o at approximately95 minutes into the process. However, new carriers 116 of wafers 118 cannot be loaded into first input/output chamber 102 and secondinput/output chamber 104 at the 95 minute point because there is notenough time to transfer these wafers out of the carriers before thewafers of the previous batch illustrated in second graph 214 need to beloaded back into carriers of first input/output chamber 102 and secondinput/output chamber 104 (starting at about 173 minutes and ending atabout 190 minutes). From the second graph 214 it can be determined thatit takes approximately 95 minutes to fully unload the carriers in bothfirst and second input/output chamber 102 and 104. From the first graph212 it can be seen that the last wafer 118 is loaded back into thesecond input/output chamber 104 at about 190 minutes. If new cassettesare to be loaded immediately after the wafers 118 of second graph 214are transferred out of first and second input/output chamber 102 and 104at point 3 o and before the wafers are transferred back to the carriersfor first graph 212, the new cassettes must be in place and all wafersremoved within 95 minutes. However, of those 95 minutes, duringapproximately 45 minutes robot arm 120 is busy transferring wafers fromHF etching station 108 to staging station 110 and from staging station110 to oxidation station 112 for second graph 214 and to transfer wafersfrom LPCVD station 114 to staging station 110 for first graph 212. Thisleaves only 50 minutes to transfer new wafers 118 from the first andsecond input/output chambers 102 and 104 to the HF etching station 118,which is not possible. Thus, new carriers of wafers cannot be loadedinto first and second input/output chamber 102 and 104 until there istime to start the processing. This occurs at about 290 minutes, wherethird graph 216.

[0046] The above discussion illustrates how the present invention can beused as an analytical tool. In a manual embodiment, a user couldmanually layout a complete process using a drawing program such as VISIOby Microsoft Inc., of Redmond Wash. Then, based on the knowledge of theprocesses and the constraints formed by the initial graph, the usercould overlay other graphs representing the starting of a new processcycle. The user might determine that certain waiting periods, such aspoint 232 of first graph 212 needs to be added. In this way the user canform prototypes of potential wafer process station uses. Similarplanning can be done if the graphing is done automatically using asimulation of cluster tool 100 or the data from an actual cluster tool100. In case of an actual process being captured in real time, thegraphs represent what is actually happening in the system. Once thegraph of one batch is determined, it can be examined to determine when anew batch can be initiated. Also, it can be examined for places wherepotential bottlenecks may occur.

[0047] Also illustrated in process station area 202 of graphical display200 is a row for the wafer handling chamber. Associated with the row forthe wafer-handling chamber 106 is a plurality of wafer handlingindicators 250-272. The position of the indicators represent when thewafer-handling chamber is in use. The wafer-handling chamber 106 is inuse when wafers 118 are being transferred from one process station toanother. For example, indicator 358 represents wafer handling chamber106 being used for second graph 214 to transfer wafers 118 from HFetching station 108 to staging station 110 and from staging station 110to oxidation station 112 and for the use of wafer handling station 106to transfer wafers 118 from LPCVD station 114 to staging station 110 asseen in first graph 212. The wafer handling indicators 250-272 providean operator with the ability to see when the wafer-handling chamber 106is being used for planning purposes.

[0048]FIG. 4 is a flowchart illustrating the generation of a graphicalrepresentation of a semiconductor process. In step 302 it is determinedwhere the wafers 118 are located. This can be accomplished using varioussensors in the process stations. At the start of a process, wafers 118are initially in carriers 116 in first input/output chamber 102 andsecond input/output chamber 104. As an alternative for detecting thewafer locations by sensors, it is possible to start with a knownstarting condition and keep track of the wafer movements and locationsthrough the cluster tool controller. In most practical situations, acombination of sensing and tracking will be applied. Sensing thepresence of each wafer in each input/output chamber is standard practicein cluster tools. Sensing the presence of a wafer at other locationsdepends on the complexity and feasibility of such sensing. In hightemperature stations and batch stations it is practically impossible tosense the location of each wafer present in the station. However,sensing each wafer upon insertion into or withdrawal from the station iseasier to carry out. By keeping track of the wafer transfers inside thestation the position of all the wafers inside the station can be known.

[0049] After determining the location of the wafers, in a next step 304,the drawing of a line segment in a first direction is initiated. Theline segment in one embodiment is a horizontal line segment. Thethickness of the line segment is representative of the number of wafersin the process station. The length of the line segment represents thetime spent in a process station. The position of the line segment alonga vertical axis is representative of the location of the wafers.

[0050] In a next step 306, it is determined if wafers 118 remain arestill residing in a process station or if wafers 118 are transferringout of a process station. If transfer of the wafers 118 has not beeninitiated, it is determined in step 307 if the process in the processstation has been completed. If not, in step 308 the line segment in thefirst direction is continued with a straight line. If the process in thestation has been completed, in step 309 the line segment in the firstdirection is continued with a dotted line to indicate that the processis completed but transfer of the wafers 118 has not initiated.

[0051] If transfer of wafers 118 has been initiated, in step 310 asecond line segment in a second direction is initiated. The second linesegment, in one embodiment, is connected with and perpendicular to theline segment in the first direction. In one embodiment, the line segmentextends in a vertical direction. The width of the line segmentrepresents the amount of time it takes to transfer the wafers from oneprocess station to another. The starting position of the line segment inthe vertical direction represents the starting location of the transferat a first process station and the end portion represents thedestination location at another process station. In step 312, it isdetermined if the transfer is complete. If the transfer is not complete,then, in step 314, the line segment continues to be generated. If thetransfer is complete, in step 316 it is determined if the overallprocess is complete. If the process is complete then the line of theoverall process terminates in step 318. If the process is not complete,then the generation of a new line segment in a first direction isinitiated in step 304. Then new line segment will be connected to thesecond line segment.

[0052] Having now described preferred embodiments of the inventionmodifications and variations may occur to those skilled in the art. Theinvention is thus not limited to the preferred embodiments, but isinstead set forth in the following clauses and legal equivalentsthereof.

What is claimed is:
 1. A method for generating a graphicalrepresentation of a processing system in which one or more work piecesare processed in a number of process stations comprising: forming afirst line segment in a first direction, the first line segmentindicating the time one or more work pieces spends in a first processstation; and forming a second line segment connected to the first linesegment in a second direction, the second line segment representing thetransfer of the one or more work pieces from the first process stationto a second process station.
 2. The method of claim 1 wherein the stepof forming a first line segment further comprises forming a first linesegment wherein the thickness of the line segment represents the numberof work pieces in the first process station.
 3. The method of claim 1wherein the step of forming a second line second comprises forming asecond line segment wherein the thickness of the second line segmentrepresents the time taken to transfer the work pieces between the firstprocess station and the second process station.
 4. The method of claim 1further comprising the step of forming additional line segments in afirst direction to represent time work pieces spend in additionalprocess stations
 5. The method of claim 1 further comprising the step offorming additional line segments in a second direction to represent thetransfer of work pieces from one process station to another processstation, the additional vertical lines connecting an end of processingin one process station and a beginning of processing in another processstation.
 6. The method of claim 1, further comprising using a differentcolor to represent work pieces belonging to a different batch.
 7. Themethod of claim 1 wherein the step of forming a first line segment andthe step of forming a second line segment further comprises forming afirst line segment in response to data generated by a processing tooland forming a second line segment in response to data generated by theprocessing tool.
 8. The method of claim 1 wherein the step of forming afirst line segment and the step of forming a second line segment furthercomprises forming a first line segment in response to data generated bya simulator and forming a second line segment generated by a datagenerated by a simulator.
 9. The method of claim 1 further comprisinggenerating additional graphical representations of a processing systemfor a different batch of work pieces.
 10. A method for graphicallyrepresenting the progress of one or more wafers being processed in aplurality of process stations comprising: determining the start of afirst process performed on one or more wafers in one of the plurality ofprocess stations; initiating the generation of a first line segment in afirst direction corresponding to the start of the process in one of theplurality of process stations; determining the end of the first processin one of the plurality of process stations; terminating the first linesegment; determining the start of a transfer of one or more wafers fromone of the plurality of process stations to another one of the pluralityof process stations; initiating the formation of a second line segmentin a second direction substantially perpendicular to the first linesegment and connected to the first line segment; determining thecompletion of the transfer of the one or more wafers; terminating theformation of the second line segment; and repeating the step ofdetermining the start of a process.
 11. The method of claim 10 whereinthe step of initiating the generation of a line segment furthercomprises initiating the generation of a line segment wherein thethickness of the line segment is indicative of the number of wafers inthe first process station.
 12. The method of claim 10, wherein the stepof initiating the formation of a line segment substantiallyperpendicular to the first axis comprises initiating the formation of aline segment substantially perpendicular to the first axis wherein thethickness of the second line segment is proportional to the time takento transfer the wafers.
 13. The method of claim 10, wherein the wafersare contained in one or more carriers.
 14. The method of claim 13further comprising using a different color to represent wafers belongingto a different batch of wafers.
 15. The method of claim 10 wherein theprocess stations are part of a cluster tool.
 16. A display coupled to acontroller for showing a graphical representation of a process involvinga plurality of process stations in the manufacture of one or more workpieces comprising: a graph area to display the graphical representation,the graphical representation comprising: a plurality of line segments ina first direction, the length of the line segments in the firstdirection indicative of the time one or more work pieces spend in one ofthe plurality of process stations; and a plurality of line segments in asecond direction, the line segments in the second direction connectingthe line segments in the first direction, the line segments in thesecond direction representing the transfer of one or more work piecesfrom one of the plurality of process stations to another one of theplurality of process stations.
 17. The display of claim 16 wherein twoor more graphical representations are included in the graph area, eachof the graphical representation representing the processing of adifferent batch of work pieces.
 18. The display of claim 17 wherein eachgraphical representation is displayed using a different color orshading.
 19. The display of claim 16 wherein the graphicalrepresentation is formed in response to data generated by a processingtool.
 20. The graphical display of claim 16 wherein the graphicalrepresentation is formed in response to data generated by a simulator.21. A manufacturing system comprising: a process tool having a pluralityof process stations that perform manufacturing steps on a plurality ofwork pieces; a controller coupled to the process tool to send controlcommands to the process tool; a display coupled to the controller, thedisplay receiving data from the controller regarding the processing ofthe plurality of work pieces in the process tool, the display having agraph area to display a graphical representation of the processing ofthe work pieces, the graphical representation comprising: a plurality ofline segments in a first direction, the length of the line segments inthe first direction indicative of the time one or more work pieces spendin one of the plurality of process stations; and a plurality of linesegments in a second direction, the line segments in the seconddirection connecting the line segments in the first direction, the linesegments in the second direction representing the transfer of one ormore work pieces from one of the plurality of process stations toanother one of the plurality of process stations.
 22. The system ofclaim 21 wherein two or more graphical representations are included inthe graph area, each of the graphical representation representing theprocessing of a different batch of work pieces.
 23. The system of claim22 wherein each graphical representation is displayed using a differentcolor or shading.
 24. The system of claim 21 wherein the graphicalrepresentation is formed in response to data generated by a processingtool.
 25. The system of claim 21 wherein the graphical representation isformed in response to data generated by a simulator.
 26. A semiconductorwafer manufacturing system comprising: a cluster tool having a pluralityof process stations that perform manufacturing steps on a plurality ofsemiconductor wafers; a controller coupled to the cluster tool to sendcontrol commands to the cluster tool; a display coupled to thecontroller, the display receiving data from the controller regarding theprocessing of the plurality of semiconductor wafers in the process tool,the display having a graph area to display a graphical representation ofthe processing of the semiconductor wafers, the graphical representationcomprising: a plurality of line segments in a first direction, thelength of the line segments in the first direction indicative of thetime one or more semiconductor wafer spend in one of the plurality ofprocess stations; and a plurality of line segments in a seconddirection, the line segments in the second direction connecting the linesegments in the first direction, the line segments in the seconddirection representing the transfer of one or more semiconductor waferfrom one of the plurality of process stations to another one of theplurality of process stations.
 27. The system of claim 26 wherein two ormore graphical representations are included in the graph area, each ofthe graphical representation representing the processing of a differentbatch of wafers.
 28. The system of claim 27 wherein each graphicalrepresentation is displayed using a different color or shading.
 29. Thesystem of claim 26 wherein the graphical representation is formed inresponse to data generated by a simulation of a cluster tool.
 30. Aprogram product comprising: a computer readable storage medium forstoring instructions that, when executed by a computer causes thecomputer to perform a method for generating a graphical representationof a processing system in which one or more work pieces are processed ina number of process stations comprising: computer readable program codefor forming a first line segment in a first direction, the first linesegment indicating the time one or more work pieces spends in a firstprocess station; and computer readable program code for forming a secondline segment connected to the first line segment in a second direction,the second line segment representing the transfer of the one or morework pieces from the first process station to a second process station.31. The program product of claim 30 wherein the computer readableprogram code for forming a first line segment further comprises computerreadable program code for forming a first line segment wherein thethickness of the line segment represents the number of work pieces inthe first process station.
 32. The program product of claim 30 whereinthe computer readable program code for forming a second line secondcomprises computer readable program code for forming a second linesegment wherein the thickness of the second line segment represents thetime taken to transfer the work pieces between the first process stationand the second process station.
 33. The program product of claim 30further comprising computer readable program code for forming additionalline segments in a first direction to represent time work pieces spendin additional process stations.
 34. The program product of claim 30further comprising computer readable program code for forming additionalline segments in a second direction to represent the transfer of workpieces from one process station to another process station, theadditional vertical lines connecting an end of processing in one processstation and a beginning of processing in another process station. 35.The program product of claim 30 further comprising computer readableprogram code for using a different color to represent work piecesbelonging to a different batch.
 36. The program product of claim 30wherein the computer readable program code for forming a first linesegment and the computer readable program code for forming a second linesegment further comprises computer readable program code for forming afirst line segment in response to data generated by a processing tooland computer readable program code for forming a second line segment inresponse to data generated by the processing tool.
 37. The programproduct of claim 30 wherein the computer readable program code forforming a first line segment and the computer readable program code forforming a second line segment further comprises computer readableprogram code for forming a first line segment in response to datagenerated by a simulator and computer readable program code for forminga second line segment generated by a data generated by a simulator. 38.The program product of claim 30 further comprising computer readableprogram code for generating additional graphical representations of aprocessing system for a different batch of work pieces.